The present invention relates to an adjustment assembly for positioning a valve spool and its associated centering spring within the bore of a valve body.
A power steering assembly for a marine drive employs a hydraulic assist to reduce steering loads to the operator. The steering arm of the marine drive is connected to a piston rod clevis of a hydraulic cylinder and the housing of the cylinder in turn is anchored to the boat. The steering wheel of the boat is connected through a steering cable to a movable valve that controls the direction and flow magnitude of the hydraulic fluid provided to the hydraulic cylinder. The operator of the boat thus needs only to exert enough effort to operate the valve and not that required to actually steer the boat. The hydraulic valve utilized in such a system is comprised of a valve body having a number of ports spaced along its length and containing a spool receiving bore. The spool is provide with a number of grooves and lands that cooperate with the various ports in the valve body to direct the flow of hydraulic fluid.
Typically, the valve spool has an associated centering spring which returns the valve spool to a neutral position when no external forces are applied to the spool. When assembling the valve or replacing parts within the valve, it is necessary that the valve spool be placed within the valve body at a very precise position so that the lands and grooves are precisely aligned with their associated ports in the valve body. Without such precise alignment, undesirable leakage would occur between the various ports.
A prior adjustment assembly described in U.S. Pat. No. 4,595,370 to Small utilized a snap ring to position the centering spring on an adjustment sleeve threaded into the valve body. This arrangement was difficult to manufacture and use because of clearance in the screw threads and the snap ring grooves. Further, a seal was loaded by the centering spring and could hang up in use.
Thus, it is an object of the present invention to provide an adjustment assembly that allows for the exact positioning of the valve spool within the valve body.